Did they mention the “immortal jellyfish”?
After reproducing, they revert to infancy and start aging again.
http://en.wikipedia.org/wiki/Turritopsis_dohrnii
If you think they can do this because they are simple organisms, humans have 46 chromosome pairs. Some jellyfish have as many as 216 chromosome pairs. Many have far fewer. Nobody has written how many the immortal jellyfish has.
“The eggs develop in the gonads of the female medusae”
Now, right there is your first problem.